"Americans are from Mars and Europeans are from Venus," wrote Robert Kagan in "Of Paradise and Power," published in 2003, just as the United States went into Iraq. Americans, he wrote, see themselves in "an anarchic Hobbesian world," where security and a liberal order depend on military might, while Europe is "moving beyond power into a self-contained world of laws and rules and transnational negotiation and co-operation."

A dozen years later, Europeans and not a few Americans have been asking how well Mars has been working out for America. But Americans and an increasing number of Europeans should also be asking -- when they think enough about it to ask -- how Venus is working out for Europe.

Not so well, is the obvious answer. If America's economic growth has been sluggishness, with high unemployment and withdrawal from the work force, most of Europe hasn't been growing at all, with unemployment, especially among the young, remaining perpetually high in much of the continent.

Europe's recoil against Mars and embrace of Venus is understandable. In the early summer of 1914 Europe seemed on top of the world, economically advanced, increasingly politically democratic, culturally confident. Then Europe plunged into what turned out to be 31 years of horrifying war, political turbulence and economic depression. Europeans lost confidence in their civilization and have never fully regained it.

After World War II, the United States jump-started Western Europe's economies and provided a security guarantee against the Soviet Union through NATO. It encouraged first the Common Market, to join together the habitual enemies France and (West) Germany, and later the European Union.

In the quarter-century after 1945, Western Europe recovered economically, growing faster than the United States, and drew closer to achieving American standards of living. Then, around 1970, Western Europe used its regained prosperity to finance leisure -- fewer working hours, longer vacations, early retirements -- while Americans started working longer hours and producing more.

With the fall of Communism in 1989-91 Europe's problems seemed solved. NATO and the EU could be, and were with considerable success, expanded east to include Soviet satellites and the three Baltic republics.

There seemed no need to fight violent wars or risk nuclear annihilation anymore. No need to work very hard: The welfare state will provide. No need to have many children: Most nations' birth rates fell below replacement, leaving fewer workers to pay for those welfare benefits in the then-distant future.

Problems would be solved by mandarins, operating with minimal democratic feedback out of EU offices in Brussels. Their favorite solution for powering Europe's economies was a single currency, the euro. Most of Europe joined; Britain, thanks to Chancellor of the Exchequer Gordon Brown, stayed out.

This Venusian Europe supposed that violence and genocide in the former Yugoslavia could be quelled by conferences and resolutions. It turned out to take air power and ground troops, eventually provided by the United States.

After the Sept. 11 attacks, much of Europe joined the United States in Afghanistan and Iraq. But most European nations' military contributions were minimal, and Europe soon tired of these seemingly unwinnable wars. Mars seemed in decline, Venus in the ascendant.

The 2008 financial crisis and the increasing aggression of Vladimir Putin's Russia have been disastrous for the Venus dream. The euro proved to be a misbegotten project: a single currency for stubbornly diverse nations with different economic needs has produced not prosperity and unity, but stagnation and division.

The resulting crisis has dragged even Germany, with its strong work ethic and reformed labor laws, down to zero growth, while youth unemployment is around 50 percent in Southern Europe and bank deposits are rapidly oozing out of Greece.

And the dream of expanding NATO and the EU ever eastward has run up against someone with quite another vision. Russian troops gobbled up part of Georgia in 2008. Only thinly disguised, they have been ravaging Ukraine since February 2014. Russia annexed Crimea last March.

Europe's response has been Venusian, as has been the Obama administration's, despite the American and British guarantee of Ukraine's borders in the 1994 Budapest Memorandum. Military intervention is ruled out; military aid has been limited to things like Meals Ready to Eat and winter blankets.

There's a danger that Putin will move surreptitiously into the Baltic states -- NATO members whom the alliance is pledged to defend. It's hard to live like Venus when Mars is marching into your neighborhood.